Implements in-flight abort for soft-deleted tasks across all three execution lanes: executor, merger, and triage now check for `deletedAt` before proceeding and emit `task:soft-delete-in-flight-abort` audits rather than continuing work on a deleted task. The 829-line addition is dominated by integra
Fusion-Task-Id: FN-5264
Fusion-Task-Lineage: 4ee8e63b-abf0-43e2-9130-39a05434d8f9